Disposable diaper with thermoplastic material anchored hook fastener portion

ABSTRACT

A hook fastener portion for use in a hook and loop fastener that has a woven backing with portions of pile monofilaments projecting from its front surface providing hooks adapted for making releasable engagement with loops of the fastener. Only a layer of thermoplastic material along a rear surface of the backing and the mechanical engagement of the portions of the pile monofilaments woven into the backing anchor the monofilaments in the backing, and that layer of thermoplastic material can be a hot melt adhesive used to adhere the hook fastener portion to a substrate.

This is a division of application Ser. No. 07/438,693 filed Nov. 17,1989, now U.S. Pat. No. 5,100,400.

TECHNICAL FIELD

The present invention relates to disposable diapers including hook andloop fasteners, and in particular to the hook portions of suchfasteners.

BACKGROUND ART

Disposable diapers including hook and loop fasteners for fasteningtogether portions of the diapers to secure them to individuals are wellknown in the art. U.S. Pat. Nos. 4,410,327 and 4,568,342 provideillustrative examples. Also it is well known to use hook fastenerportions in such fasteners that have a woven backing and a plurality ofpile monofilaments with portions woven into the backing and portionsprojecting from a front surface of the backing that have distal endportions adapted for releasable engagement with loops included in thefasteners (e.g., by forming arcuate hook portions or mushroom shapedheads at their ends), and a layer of adhesive along a rear surface ofthe backing adhering the hook fastener portions in place.

Heretofore, however, such woven hook fastener portions have been made ina continuous strip by a method including a weaving step to form thewoven backing with portions of the pile monofilaments woven therein, ahook forming step in which arcuate hook portions or heads are formed onthe projecting portions of the pile monofilaments, an autoclave step inwhich the woven fasteners are exposed to steam in an autoclave to shrinkthe backing, a binder coating step in which a coating of a liquid bindermaterial for adhering together the warp and weft yarns and the woven inportions of the pile monofilaments is applied to the backing, and adrying step that takes about 48 hours in which the binding material onthe backing is dried and cured; after which an adhesive for adhering thebacking in place may be applied along the rear surface of the backingand the strip may be slit and/or cut to provide a hook fastener portionof a desired size for its intended application. While this method hasproduced a very suitable hook fastener portion which can withstand beingopened and closed many times and being washed as is required for manyuses, the number of steps it entails, and the batch nature of many ofthe steps it includes adds significantly to its cost. Thus, the hookfastener portion produced by that method is very high priced compared tohook fastener portions made by other methods such as continuous moldingtechniques that, while not of the high quality of the woven hookfastener portions made by the method described above, are still quiteadequate for use in fasteners intended for certain uses, such as ondisposable garments (e.g., disposable diapers) where a limited number ofengagements and disengagements of the fasteners are anticipated.

DISCLOSURE OF INVENTION

The present invention provides a hook fastener portion with a wovenbacking that is significantly less expensive to make than the hookfastener portions with woven backings made by the method describedabove, and is quite adequate for use in fasteners intended for certainuses, such as on disposable garments (e.g., disposable diapers) where alimited number of engagements and disengagements of the fasteners areanticipated.

According to the present invention there is provided an inexpensive hookfastener portion adapted for use in hook and loop fastener means, suchas on a disposable diaper of the type including a laminate having firstand second opposite ends, and the hook and loop fastener means forfastening together portions of the laminate to secure the diaper to anindividual including loop fastener portion means adjacent the first endof the laminate comprising a multiplicity of loops, and the hookfastener portion at the second end of the laminate. The hook fastenerportion comprises a plurality of warp yarns, a plurality of weft yarnsinterwoven with the warp yarns to form with the warp yarns a wovenbacking having front and rear major surfaces, a plurality of pilemonofilaments having portions woven into the backing and portionsprojecting from the front surface of the backing and having distal endportions adapted for making releasable engagement with the loops, and alayer of thermoplastic material along the rear surface of the backing.Only the layer of thermoplastic material and the mechanical engagementof the portions of the pile monofilaments woven into the backing withthe warp and weft yarns anchor the monofilaments in the backing. Also,the layer of thermoplastic material can serve as or be a hot meltadhesive adapted to adhere the hook fastener portion to a substrate suchas the laminate of the diaper.

Preferably the pile monofilaments are of larger diameter than the warpand weft yarns and include portions passing around weft yarns thatprotrude along the rear surface of the woven backing, and the layer ofthermoplastic material is discontinuous and formed of discrete layerportions located around the protruding portions of the pilemonofilaments and adhering the protruding portions of the pilemonofilaments to adjacent portions of the warp and weft yarns.

When the hook fastener portion is intended to be attached to apolyethylene sheet included in the laminate of a disposable diaper, thelayer of thermoplastic material is preferably an ethylene vinyl acetatehot melt adhesive weighing in the range of 2 to 12 grains per 4 inch by6 inch area, and preferably weighing at least 4.5 grains per 4 inch by 6inch area, with 5.5 grains per 4 inch by 6 inch area being a preferredweight which is selected as a compromise that provides both firmadhesion of the hook fastener portion to the layer of polyethylene, andlow cost for the layer of hot melt adhesive. Such hook fastener portionscan be easily attached to the polyethylene sheet using moderate pressureand conventional heat application or ultrasonic attaching techniques.

Also, when the hook fastener portion is intended to be used as part ofthe fastener for a disposable diaper, preferably the weft and warp yarnsare of polyester (e.g., 150-34 denier polyester) and the pilemonofilaments are of polypropylene (e.g., 0.004 to 0.010 inch diameter);and the backing of the hook fastener portion has in the range of 28 to42 weft yarns crossing the warp yarns per inch of length of the warpyarns, with about 32 weft yarns crossing the warp yarns per inch oflength of the warp yarns being preferred. It expected that such hookfastener portions having even lower numbers of weft yarns may be usefulfor certain purposes.

BRIEF DESCRIPTION OF DRAWING

The present invention will be further described with reference to theaccompanying drawing wherein like reference numerals refer to like partsin the several views, and wherein:

FIG. 1 is a perspective view of a disposable diaper including hookfastener portions according to the present invention;

FIG. 2 is a much enlarged fragmentary perspective view of one of thehook fastener portions of FIG. 1 before it is attached to the diaper ofFIG. 1;

FIG. 3 is an enlarged photographic fragmentary top view of one of thehook fastener portions of FIG. 1 before it is attached to the diaper ofFIG. 1;

FIG. 4 is an enlarged photographic fragmentary bottom view of one of thehook fastener portions of FIG. 1 before it is attached to the diaper ofFIG. 1; and

FIG. 5 is a schematic view of a method for making the hook fastenerportions of FIG 1.

DETAILED DESCRIPTION

Referring now to the drawing, there is shown in FIG. 1 a disposablediaper 10 including two hook fastener portions according to the presentinvention generally designated by the reference numeral 12.

Generally the disposable diaper 10 includes a laminate 14 having firstand second opposite ends, and hook and loop fastener means for fasteningtogether portions of the laminate 14 to secure the diaper 10 to anindividual. The fastener means includes loop fastener portion meansadjacent the first end of the laminate that could be provided by aportion of the laminate, but as illustrated comprises a loop fastenerportion 15 adhered to the laminate 14 and having a multiplicity of loopsprojecting from its surface opposite the laminate 14; and the two spacedhook fastener portions 12 at the second end of the laminate 14.

As is best seen in FIGS. 2 and 3, the hook fastener portion 12 comprisesa plurality of generally parallel warp yarns 16 (e.g., 156 warp yarnsper inch), a plurality of generally parallel weft yarns 18 interwovenwith the warp yarns 16 at right angles thereto (e.g., 28 to 42 andpreferably 32 weft yarns per inch measured along the warp yarns) to formwith the warp yarns a woven backing 20 having front and rear majorsurfaces 21 and 22, and a plurality of pile monofilaments 24 (e.g.,twenty four 0.004 to 0.010 inch diameter polypropylene monofilaments 24per inch of width measured along the weft yarns 18). The pilemonofilaments 24 have portions woven in a "plane weave" manner shown inFIGS. 2, 3 and 4 into the backing 20, in which "plane weave" manner thewoven in portions of the monofilaments 24 pass over 1 and under 2 weftyarns 18 and extend parallel to the warp yarns 16. The pilemonofilaments 24 also include portions projecting from the front surface21 of the backing and having generally semi cylindrical or mushroomshaped heads 25 at their distal ends (e.g., 112 to 168 and preferably128 projecting portions per square inch). Also included in the hookfastener portion 12 is a discontinuous layer 26 of thermoplasticmaterial along the rear surface 22 of the backing 20 with only the layer26 of thermoplastic material and the mechanical engagement of theportions of the pile monofilaments 24 woven into the backing 20 aroundand intertwined with the warp and weft yarns 16 and 18 anchoring thepile monofilaments 24 in the backing 20, and the layer 26 ofthermoplastic material also providing means for adhering the fastenerportion 12 to the laminate 14.

As can best be seen in FIG. 4, the pile monofilaments 24 are ofsubstantially larger diameter than the stranded warp and weft yarns 16and 18 and include portions 27 passing around weft yarns 18 thatprotrude along the rear surface 22 of the woven backing 20 because oftheir larger diameter and stiffness and because they remain round whilethe yards can flatten as they pass around another yarn. The layer ofthermoplastic material 26 is discontinuous and formed of discrete layerportions 28 that are located around the protruding portions 27 of thepile monofilaments 24 and adhere the protruding portions 27 of the pilemonofilaments 24 to adjacent portions of the warp and weft yarns 16 and18.

Although other thermoplastic materials such as "JET MELT" hot meltadhesives commercially designated 3762LM and 3792LM and available fromMinnesota Mining and Manufacturing Company, St. Paul, Minn. or the hotmelt adhesive commercially designated 7199D available from BosticDivision, Middleton, Mass., could be used as the layer 26 ofthermoplastic material; a presently preferred thermoplastic material orhot melt adhesive described in U.S. Pat. No. 4,710,190 (the contentwhereof is incorporated herein by reference) consists of 60 percent byweight of an ethylene vinyl acetate adhesive (e.g., the adhesivecommercially designated "Elvax 210" available from E. I. dupontdeNemours and Company, Wilmington, Del., and 40 percent by weight of asuitable tackifyer (e.g., the tackifyer commercially designated"Piccolyte HM-90" available from Hercules Incorporated, MidwesternRegion, Naperville, Ill., to which total weight of that mixture is added1 percent of an antioxidant (e.g., the antioxidant commerciallydesignated "Irganox 1010" available from Ciba-Geigy Corporation,Hawthorne, N.Y.

FIG. 5 illustrates a method according to the present invention formaking the hook fastener portion 12. Generally, that method includes thewell known steps of weaving the warp yarns 16, weft yarns 18, and pilemonofilaments 24 together to form from the woven backing 20 withportions of the pile monofilaments 24 projecting from its front surface21 using a weaving machine 30 (e.g., either a model NF 53/66 weavingmachine available from Jacob Muller of America, Charlotte, N.C. whichforms the projecting portions of the pile monofilaments 24 into loopsprojecting from the front surface 21 of the backing 20, or a model NB 40machine also available from Jacob Muller of America which simultaneouslyforms two parallel backings 20 with separate sets of warp and weft yarns16 and 18, and weaves portions of a single set of pile monofilaments 24into both backings 20 in a plane weave manner with portions of thosemonofilaments extending at right angles to and between opposed frontsurfaces 21 of the backings 20); and heating the projecting portions ofthe pile monofilaments 24 to form the heads 25 on their distal ends.Such head 25 forming when the backing 20 is formed by the model NF 53/66weaving machine described above and illustrated in FIG. 5 is done byheating the center of the loops with a heated wire 32 so that the loopseach will separate into two projecting portions of the monofilament 24each with a head 25 at its distal end; and such head 25 forming when thebacking 20 is formed by the model NB 40 weaving machine described aboveis done by heating the central parts of the portions of themonofilaments 24 extending between the backings 20 with a heated wire sothat each portion will separate into two projecting portions of themonofilament 24 (one projecting from each backing 20), each with a head25 at its distal end. The method then includes the further step ofcoating a layer 26 of thermoplastic material or hot melt adhesive alongthe rear surface 22 of the backing 20 so that only the layer 26 ofthermoplastic material and the mechanical engagement of the portions ofthe pile monofilaments 24 woven into the backing 20 with the warp andweft yarns 16 and 18 anchor the monofilaments 24 in the backing 20. Thiscoating step is performed by passing the woven backing 20 with theheaded portions of the pile monofilaments 24 through a hot melt coatingdevice 34, (e.g., made using the Model GRO72X1 hot melt pump and dieassembly available from Meltex Corporation, Peachtree City, Ga. 30269),which can advantageously be done as that structure leaves the weavingmachine 30 so that the weaving, heating and coating steps describedabove are done continuously on the same production line.

Preferably, as illustrated, that hot melt coating device 34 comprises arubber back up roll 36 around which the backing 20 passes with its frontsurface 21 adjacent the back up roll 36, and an extrusion die 38 havinga guide surface 39 and an elongate slot 40 extending transversely theentire width of the backing 20 along the rear surface 22 of the backing20 as the backing moves across the die 38. Thermoplastic material fromwhich the layer 26 is formed is pumped to the die 38 and through theslot 40 from a heated pail unloading pump 42 included in the hot meltpump and die asembly at a rate related to the speed of movement of thebacking 20 across the die 38. The portions 27 of the pile monofilaments24 that protrude along the rear surface 22 of the backing 20 wipe awaythe thermoplastic material exiting from the outlet slot 40 of the die 38and cause the layer 26 of thermoplastic material to be discontinuous andformed of the discrete layer portions 28 located around the protrudingportions 27 of the pile monofilaments 24. From the die 38 the rearsurface 22 of the backing 20 passes through a nip between the roller 36and a silicone rubber coated first water cooled roller 44 and around theroller 44 so that the layer portions 28 cool, solidify, and adhere theprotruding portions 27 of the pile monofilaments 24 to adjacent portionsof the warp and weft yarns 16 and 18. The nipped rollers 36 and 44engage the adhesive coated backing 20, and one of them is driven to movethe backing 20 through the hot melt coating device 34. The front surface21 of the adhesive coated backing 20 then passes around a siliconerubber surface of a second water cooled roller 46 after which it may beslit and cut to length (not shown) to provide a multiplicity of the hookfastener portions 12. Subsequently, the hook fastener portions 12 may beattached to the laminate 14 of a disposable diaper 10 through theapplication of heat and pressure.

The present invention has now been described with reference to oneembodiment thereof. It will be apparent to those skilled in the art thatmany changes can be made in the embodiment described without departingfrom the scope of the present invention. Thus the scope of the presentinvention should not be limited to the structure described in thisapplication, but only by structures described by the language of theclaims and the equivalents of those structures.

We claim:
 1. A method for making a hook fastener portion comprising thesteps ofweaving warp yarns, weft yarns, and pile monofilaments togetherto form from the warp and weft yarns and portions of the pile filamentsa woven backing with front and rear major surfaces and portions of thepile monofilaments projecting from the front surface of the wovenbacking, said weaving step being done using pile monofilaments that areof larger diameter than the warp and weft yarns to provide portions ofthe pile monofilaments passing around weft yarns that protrude along therear surface of the woven backing; adapting the projecting portions ofthe pile monofilaments to make releasable engagement with loops; andcoating a layer of thermoplastic material along the rear surface of thebacking so that only the layer of thermoplastic material and themechanical engagement of the portions of the pile monofilaments woveninto the backing with the warp and weft yarns anchor the monofilamentsin the backing, said coating step comprising:providing a die having agenerally planar guide surface and an elongate outlet opening throughthe guide surface, feeding the thermoplastic material at a predeterminedrate through the outlet opening, and moving the rear surface of thewoven backing along the guide surface and over the outlet opening at apredetermined rate of movement related to the rate of feeding of thethermoplastic material and with the outlet opening extending transverseto the direction of movement of the woven backing so that the protrudingportions of the of the pile monofilaments wipe the thermoplasticmaterial from the outlet opening and cause the layer of thermoplasticmaterial to be discontinuous and formed of discrete layer portionslocated around the protruding portions of the pile monofilaments thatadhere the protruding portions of the pile monofilaments to adjacentportions of the warp and weft yarns.
 2. A method for making a hookfastener portion for use on a disposable garment and attaching the hookfastener portion to a substrate of the garment, said method comprisingthe steps ofweaving warp yarns, weft yarns, and pile monofilamentstogether to form from the warp and weft yarns and portions of the pilefilaments a woven backing with front and rear major surfaces and havinggenerally in the range of 28 to 42 weft yarns crossing the warp yarnsper inch of length of the warp yarns, and portions of the pilemonofilaments projecting from the front surface of the woven backing,said weaving step being done using pile monofilaments that are of largerdiameter than the warp and weft yarns to provide portions of the pilemonofilaments passing around weft yarns that protrude along the rearsurface of the woven backing; adapting the projecting portions of thepile monofilaments to make releasable engagement with loops; coating alayer of thermoplastic material along the rear surface of the backing sothat only the layer of thermoplastic material and the mechanicalengagement of the portions of the pile monofilaments woven into thebacking with the warp and weft yarns anchor the monofilaments in thebacking, said coating step comprising:providing a die having a generallyplanar guide surface and an elongate outlet opening through the guidesurface, feeding the thermoplastic material at a predetermined ratethrough the outlet opening, and moving the rear surface of the wovenbacking along the guide surface and over the outlet opening at apredetermined rate of movement related to the rate of feeding of thethermoplastic material and with the outlet opening extending transverseto the direction of movement of the woven backing so that the protrudingportions of the of the pile monofilaments wipe the thermoplasticmaterial from the outlet opening and cause the layer of thermoplasticmaterial to be discontinuous and formed of discrete layer portionslocated around the protruding portions of the pile monofilaments thatadhere the protruding portions of the pile monofilaments to adjacentportions of the warp and weft yarns; and applying heat and pressure tosoften and adhere the coating of thermoplastic material to saidsubstrate.
 3. A method according to claim 2 wherein said weaving,heating and coating steps are done continuously on the same productionline.
 4. A method according to claim 2 wherein said coating step coats alayer of ethylene vinyl acetate adhesive weighing in the range of 2 to12 grains per 4 inch by 6 inch area.
 5. A method according to claim 2wherein said weaving step weaves a backing having about 32 weft yarnscrossing the warp yarns per inch of length of the warp yarns.
 6. Amethod according to claim 5 wherein in said weaving step the pilemonofilaments are of 250 to 600 denier polypropylene and the warp andweft yarns are of 150-34 denier polyester, and said coating step coats alayer of ethylene vinyl acetate adhesive that weighs at least 4.5 grainsper 4 inch by 6 inch area.
 7. A method according to claim 2 wherein saidcoating step coats a layer of ethylene vinyl acetate adhesive and weighsat least 4.5 grains per 4 inch by 6 inch area.
 8. A method according toclaim 2 wherein said coating step coats a layer of ethylene vinylacetate adhesive that weighs in the range of 2 to 12 grains per 4 inchby 6 inch area.
 9. A method according to claim 2 wherein said coatingstep coats a layer of ethylene vinyl acetate adhesive that weighs about5.5 grains per 4 inch by 6 inch area.
 10. A method for making a hookfastener portion for use on a disposable garment, said method comprisingthe steps of:weaving warp yarns, weft yarns, and pile monofilamentstogether to form from the warp and weft yarns and portions of the pilefilaments a woven backing with front and rear major surfaces and havinggenerally in the range of 28 to 42 weft yarns crossing the warp yarnsper inch of length of the warp yarns, and portions of the pilemonofilaments projecting from the front surface of the woven backing,said weaving step being done using pile monofilaments that are of largerdiameter than the warp and weft yarns to provide portions of the pilemonofilaments passing around weft yarns that protrude along the rearsurface of the woven backing; adapting the projecting portions of thepile monofilaments to make releasable engagement with loops; and coatinga layer of thermoplastic material along the rear surface of the backingso that only the layer of thermoplastic material and the mechanicalengagement of the portions of the pile monofilaments woven into thebacking with the warp and weft yarns anchor the monofilaments in thebacking, said coating step comprising:providing a die having a generallyplanar guide surface and an elongate outlet opening through the guidesurface, feeding the thermoplastic material at a predetermined ratethrough the outlet opening, and moving the rear surface of the wovenbacking along the guide surface and over the outlet opening at apredetermined rate of movement related to the rate of feeding of thethermoplastic material and with the outlet opening extending transverseto the direction of movement of the woven backing so that the protrudingportions of the of the pile monofilaments wipe the thermoplasticmaterial from the outlet opening and cause the layer of thermoplasticmaterial to be discontinuous and formed of discrete layer portionslocated around the protruding portions of the pile monofilaments thatadhere the protruding portions of the pile monofilaments to adjacentportions of the warp and weft yarns; said weaving, heating and coatingsteps being done continuously on the same production line.
 11. A methodaccording to claim 10 wherein said coating step coats a layer ofethylene vinyl acetate adhesive weighing in the range of 2 to 12 grainsper 4 inch by 6 inch area.
 12. A method according to claim 10 whereinsaid weaving step weaves a backing having about 32 weft yarns crossingthe warp yarns per inch of length of the warp yarns.
 13. A methodaccording to claim 12 wherein in said weaving step the pilemonofilaments are of 250 to 600 denier polypropylene and the warp andweft yarns are of 150-34 denier polyester, and said coating step coats alayer of ethylene vinyl acetate adhesive that weighs at least 4.5 grainsper 4 inch by 6 inch area.
 14. A method according to claim 10 whereinsaid coating step coats a layer of ethylene vinyl acetate adhesive andweighs at least 4.5 grains per 4 inch by 6 inch area.
 15. A methodaccording to claim 10 wherein said coating step coats a layer ofethylene vinyl acetate adhesive that weighs in the range of 2 to 12grains per 4 inch by 6 inch area.
 16. A method according to claim 10wherein said coating step coats a layer of ethylene vinyl acetateadhesive that weighs about 5.5 grains per 4 inch by 6 inch area.